There has been conventionally known an image display device including organic electroluminescence (EL) elements in which electroluminescence is used.
In the image display device as described above, temperature of an organic EL panel changes due to temperature characteristics of a thin film transistor (TFT) and the organic EL element, and accordingly light-emitting luminance changes.
Therefore, there is proposed a technology of appropriately controlling a signal waveform, signal voltage or power supply voltage to be provided to a pixel circuit of an organic EL element to stabilize light-emitting luminance with respect to a temperature change of an organic EL panel in a wide temperature range (for example, from −20° C. to +60° C.) (for example, Japanese Patent Application Laid-Open No. 07-263142, Japanese Patent Application Laid-Open No. 2000-214824, Japanese Patent Application Laid-Open No. 2001-118676, Japanese Patent Application Laid-Open No. 2001-343932, Japanese Patent Application Laid-Open No. 2003-29710, Japanese Patent No. 3389653, Japanese Patent Application Laid-Open No. 2003-150113, Japanese Patent Application Laid-Open No. 2003-330419, Japanese Patent Application Laid-Open No. 2004-102077, Japanese Patent Application Laid-Open No. 2005-55909, Japanese Patent Application Laid-Open No. 2005-208228, Japanese Patent Application Laid-Open No. 2005-242115, Japanese Patent Application Laid-Open No. 2005-309232 and Japanese Patent Application Laid-Open No. 2005-316139). For example, when the signal waveform is changed for each temperature segment in increments of approximately 3° C., luminance can be suppressed from fluctuating to such an extent that a luminance change is not apparent even between temperature segments.
However, a manner in which temperature of the organic EL panel is measured to adjust luminance with respect to a temperature change thereof is adaptable to a temperature change in an initial state, but is not adaptable to a characteristic change over time due to degradation of the organic EL panel or the like. That is, the light-emitting luminance of the image display device cannot be kept constant for the same image data when a characteristic of the TFT or the organic EL element changes over time.
Further, when light-emitting is controlled in accordance with a temperature change, there is required a certain length of period for the temperature of the organic EL panel to follow the temperature change after the control, which is likely to result in a delay in control.
The problems as described above are typically common in image display devices in which light-emitting luminance changes due to a characteristic change over time or temperature change.